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High Isolated 10-MIMO Antenna Elements for 5G Mobile Applications
(2023) Ghawbar, Fayad; S, Jumadi A.; Majid, H. A.; Ghafar, Aimi S.A.; Saparudin, Faiz A.; Esmail, B. A.F.; Almohammedi, Akram A.; Ismail, Ahmad G.
The enormous increase in gadgets has resulted in a data rate shortage insufficient to satisfy the user’s needs. The multiple input multiple output (MIMO) technique is substantially deployed in the 5G wireless communication system to increase channel capacity and provide sufficient throughput. However, MIMO antennas are associated with mutual coupling, especially between closely spaced antenna elements, resulting in a low MIMO performance. Therefore, effective isolation techniques are essential to reduce the mutual coupling between the adjacent MIMO antenna elements. A hybrid decoupling technique of self-isolation and an orthogonal mode approach has been proposed to provide significant isolation for high MIMO order 5G mobile applications. A compact self-isolated 10 × 10 MIMO antenna system has been proposed for 5G mobile phone applications operating at the 3.5 GHz frequency band. The antennas act as radiating and isolating elements simultaneously, providing significant isolation. Furthermore, the self-isolated 10-MIMO antenna elements are printed on double side edges of FR-4 small substrates orthogonal to the system substrates, forming an orthogonal mode that enhances the self-decoupling approach. The s-parameters results indicate significant isolation of less than -19 dB between the adjacent 10-MIMO antenna elements. Likewise, the evaluation results of the MIMO performance metrics such as envelope correlation coefficient (ECC), diversity gain (DG), total active reflection coefficient (TARC), and channel capacity Loss (CCL), are less than 0.006, 9.97 dB, -10 dB, and 0.08 bits/s/Hz respectively. The isolation result and the evaluated MIMO performance metrics demonstrate that the proposed 10-MIMO antenna system is sufficient for 5G mobile applications.
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Life Cycle Assessment of Icelandic Volcanic Pozzolans as Low-Carbon Supplementary Cementitious Materials
(Springer Nature Switzerland AG, 2026-10-20) Hamdallah, Mohammed; Costa, Diego; Heinonen, Jukka Taneli; Christian Finger, David; Bragança, Luís; Tsikaloudaki, Katerina; Giarma, Christina; Mateus, Ricardo; Kontoleon, Karolos; Askar, Rand; Salles, Adriana; Cervantes, Camila; Faculty of Civil and Environmental Engineering
The cement industry is a major contributor to global greenhouse gas emissions, predominantly due to clinker production. Supplementary Cementitious Materials (SCMs) represent an effective mitigation strategy, yet conventional SCMs such as Fly Ash (FA) and Ground Granulated Blast Furnace Slag (GGBFS) are becoming increasingly scarce. Volcanic pozzolans offer a promising natural alternative, and Iceland possesses extensive deposits that have not yet been evaluated from an environmental perspective. This study presents the first cradle-to-gate Life Cycle Assessment (LCA) of Icelandic Volcanic Pozzolan (VPI) production, drawing on primary data from three extraction sites and a planned processing facility in Þorlákshöfn—Lambafell, Litla Sandfell, and Landeyjahöfn—and secondary data from GaBi and Ecoinvent. A declared unit of one tonne of VPI is assessed across all ReCiPe 2016 midpoint impact categories. Results show that VPI’s climate change impact of 25.5 kg CO2-eq/t falls between FA (3–10 kg CO2-eq/t) and GGBFS (50–80 kg CO2-eq/t), confirming its competitiveness with established SCMs while offering the strategic advantage of abundant local supply. Marine dredging operations emerge as the dominant environmental hotspot, accounting or approximately 48.1% of total CO2-equivalent emissions. The findings confirm VPI as a robustly low-carbon SCM and support its large-scale adoption in sustainable cement production.
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Low-fidelity model mesh density and the performance of variable-resolution shape optimization algorithms
(2012) Leifsson, Leifur; Koziel, Slawomir; Ogurtsov, Stanislav; Department of Engineering
Surrogate-based optimization (SBO) provides an interesting alternative to conventional aerodynamic shape optimization methods. By shifting the optimization burden to a cheap and yet reasonably accurate surrogate model, the design cost can be substantially reduced. SBO methods exploiting physically-based surrogates can be particularly efficient because underlying low-fidelity models embed some knowledge about the system under consideration (e.g., by sharing the simulation tools with the high-fidelity models) so that good accuracy and even better generalization capability can be obtained through a correction based on a very limited number of high-fidelity model samples. The major open problem here is the proper selection of the low-fidelity model. The type of simplifications made to construct the model, as well as its level of accuracy (e.g., mesh density) may be crucial for the algorithm performance both in terms of the quality of the final design and the computational cost of the design process. Here, we investigate this trade-off using space mapping (SM) as an exemplary SBO technique and two-dimensional airfoil shape optimization as a representative design problem. Both lift maximization and drag minimization test cases are considered.
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Knowledge-based response correction and adaptive design specifications for microwave design optimization
(2012) Koziel, Slawomir; Ogurtsov, Stanislav; Leifsson, Leifur; Department of Engineering
Simulation-based optimization has become an important design tool in microwave engineering. Yet, employing electromagnetic (EM) solvers in the design process is a challenging task, primarily due to a high-computational cost of an accurate EM simulation. This paper is focused on efficient EM-driven design optimization techniques that utilize physically-based low-fidelity models, normally based on coarse-discretization EM simulations. The presented methods attempt to exploit as much of the knowledge about the system or device of interest embedded in the low-fidelity model as possible, so as to reduce the computational cost of the design process. Unlike many other surrogate-based approaches, the techniques discussed here are non-parametric ones, i.e., they are not based on analytical formulas. The paper presents several specific methods, including those based on correcting the low-fidelity model response (adaptive response correction and shape-preserving response prediction), as well as on suitable modification of the design specifications. Formulations, application examples and the discussion of advantages and disadvantages of these techniques are also included.
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Multi-fidelity design optimization of transonic airfoils using shape-preserving response prediction
(2010) Leifsson, Leifur; Koziel, Slawomir; Department of Engineering
A computationally efficient methodology for transonic airfoil design optimization is presented. Our approach exploits a corrected physics-based low-fidelity surrogate that replaces, in the optimization process, an accurate but computationally expensive high-fidelity airfoil model. Correction of the low-fidelity model is achieved by aligning its corresponding airfoil surface pressure distributions with that of the high-fidelity model using a shape-preserving response prediction technique. The presented method is applied to airfoil lift maximization in two-dimensional inviscid transonic flow, subject to constraints on shock induced pressure drag and airfoil cross-sectional area. More than a 90% reduction in high-fidelity function calls is achieved when compared to direct high-fidelity model optimization.

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